Zoom lens

ABSTRACT

A zoom lens includes, sequentially from an object side, a positive first lens group; a negative second lens group; a positive third lens group; and a positive fourth lens group, where 2.0≦D23W/FW≦3.0 is satisfied. D23W is an interval, at a wide angle edge, between a lens that among lenses of the second lens group, is farthest on an imaging plane side and a lens that among lenses of the third lens group, is farthest on the object side. FW is a focal length of an optical system of the zoom lens at infinity focus, at the wide angle edge.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present document incorporates by reference the entire contents ofJapanese priority document, 2009-189203, 2009-189204 and 2009-189205filed in Japan on Aug. 18, 2009.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a zoom lens.

2. Description of the Related Art

In recent years, further reductions in size and increased power aredemanded of digital cameras and the like. To address these demands, acompact, high power zoom lens is proposed in Japanese Patent ApplicationLaid-Open Publication Nos. 2008-176230 and 2008-185782, for example.

The zoom lenses recited in Japanese Patent Application Laid-OpenPublication Nos. 2008-176230 and 2008-185782 are high power zoom lensesthat include at least 4 lenses, a positive lens, a negative lens, andtwo positive lenses, sequentially from an object side. In particular,the zoom lens recited in Japanese Patent Application Laid-OpenPublication No. 2008-176230 realizes an angle of view that exceeds 77°at the wide angle edge and a zoom ratio of approximately 9.4. Further,the zoom lens recited in Japanese Patent Application Laid-OpenPublication No. 2008-185782 realizes an angle of view that exceeds 61°at the wide angle edge and a zoom ratio of approximately 9.5.

Although the zoom lenses recited in Japanese Patent ApplicationLaid-Open Publication Nos. 2008-176230 and 2008-185782 achieve zoomratios of 9 or greater, the zoom lenses have a relatively large lensdiameter and thus, are not applicable to imaging apparatuses for whichgreater compactness is demanded. Furthermore, the angle of view is lessthan 80°, which is narrow and insufficient.

Moreover, the size of the zoom lenses when retracted is too large forapplication to imaging apparatuses for which reductions in size aredemanded. In addition, it cannot be said that the optical performance ofthese lenses is sufficient.

SUMMARY OF THE INVENTION

It is an object of the present invention to at least solve the aboveproblems in the conventional technologies.

A zoom lens according to one aspect of the present invention includes,sequentially from an object side, a positive first lens group; anegative second lens group; a positive third lens group; and a positivefourth lens group, where 2.0≦D23W/FW≦3.0 is satisfied. D23W is aninterval, at a wide angle edge, between a lens that among lenses of thesecond lens group, is farthest on an imaging plane side and a lens thatamong lenses of the third lens group, is farthest on the object side. FWis a focal length of an optical system of the zoom lens at infinityfocus, at the wide angle edge.

The other objects, features, and advantages of the present invention arespecifically set forth in or will become apparent from the followingdetailed description of the invention when read in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view (along an optical axis) of a zoom lensaccording to a first example;

FIG. 2 is a diagram of various types of aberration of the zoom lensaccording to the first example;

FIG. 3 is a cross sectional view (along the optical axis) of a zoom lensaccording to a second example;

FIG. 4 is a diagram of various types of aberration of the zoom lensaccording to the second example;

FIG. 5 is a cross sectional view (along the optical axis) of a zoom lensaccording to a third example;

FIG. 6 is a diagram of various types of aberration of the zoom lensaccording to the third example;

FIG. 7 is a cross sectional view (along the optical axis) of a zoom lensaccording to a fourth example;

FIG. 8 is a diagram of various types of aberration of the zoom lensaccording to the fourth example;

FIG. 9 is a cross sectional view (along the optical axis) of a zoom lensaccording to a fifth example;

FIG. 10 is a diagram of various types of aberration of the zoom lensaccording to the fifth example;

FIG. 11 is a cross sectional view (along the optical axis) of a zoomlens according to a sixth example;

FIG. 12 is a diagram of various types of aberration of the zoom lensaccording to the sixth example;

FIG. 13 is a cross sectional view (along the optical axis) of a zoomlens according to a seventh example;

FIG. 14 is a diagram of various types of aberration of the zoom lensaccording to the seventh example;

FIG. 15 is a cross sectional view (along the optical axis) of a zoomlens according to an eighth example;

FIG. 16 is a diagram of various types of aberration of the zoom lensaccording to the eighth example;

FIG. 17 is a cross sectional view (along the optical axis) of a zoomlens according to a ninth example; and

FIG. 18 is a diagram of various types of aberration of the zoom lensaccording to the ninth example.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the accompanying drawings, exemplary embodiments accordingto the present invention are explained in detail below.

A zoom lens according to an embodiment includes sequentially from theobject side, a positive first lens group, a negative second lens group,a positive third lens group, and a positive fourth lens group. The zoomlens zooms from a wide angle edge to a telephoto edge by moving thefirst to the third lens groups along the optical axis. Further, the zoomlens corrects imaging plane (image location) variation accompanying zoomand focuses the image by moving the fourth lens group along the opticalaxis.

One object of the present invention is to provide a compact zoom lensthat has a wide angle of view and high optical performance and that iscapable of high zoom ratios.

Another object of the present invention is to provide a high power zoomlens that has a wide angle of view and with respect to a retractedstate, has a thinner size than a conventional zoom lens. To achieve suchobjects, various conditions are set below.

The zoom lens according to the embodiment preferably satisfies thefollowing conditional expression, where in the zoom lens, at the wideangle edge, an interval between the lens that among the lenses of thesecond lens group, is farthest on the imaging plane side and the lensthat among the lenses of the third lens group, is farthest on the objectside is D23W and the focal length (infinity focus) of the entire opticalsystem at the wide angle edge is FW.2.0≦D23W/FW≦3.0  (1)

Conditional expression (1) prescribes a condition to reduce theeffective diameter of the first lens group while ensuring a wide angleof view of 80° or greater at the wide angle edge. Satisfaction ofconditional expression (1) enables a wide angle of 80° or greater to beachieved together with a reduced aperture of the first lens group. Belowthe lower limit of conditional expression (1), although the effectivediameter of the first lens group becomes smaller, achieving a smalleraperture of the first lens group, the maintenance of a wide angle ofview of 80° or greater becomes difficult. On the other hand, beyond theupper limit of conditional expression (1), the effective diameter of thefirst lens group becomes large at the wide angle edge, making reductionof the aperture of the first lens group difficult.

The zoom lens according to the embodiment preferably satisfies thefollowing conditional expression, where the focal length of the firstlens group is F1and the focal length of the second lens group is F2.5.7≦|F1/F2|≦10  (2)

Conditional expression (2) prescribes a condition to reduce theeffective diameter of the first lens group, increase the angle of viewat the wide angle edge, and maintain high optical performance over theentire zoom range. Below the lower limit of conditional expression (2),although high optical performance can be maintained, the effectivediameter of the lens group becomes difficult to decrease and the wideangle becomes difficult to increase. On the other hand, beyond the upperlimit of conditional expression (2), although the power of the secondlens group becomes strong, facilitating reduction of the aperture of thefirst lens group and increase of the angle of view, the correction ofvarious types of aberration becomes difficult.

The zoom lens according to the embodiment preferably satisfies thefollowing conditional expression, where the total length (distance fromthe surface farthest on the object side to the imaging plane) of theoptical system, at the wide angle edge is TaW, the total length(distance from the surface farthest on the object side to the imagingplane) of the optical system, at the telephoto edge is Tat, the halfangle of view of the optical system, at the wide angle edge is ωW, andthe maximum paraxial image height at the wide angle edge is Ymax.15≦(TaW+TaT)/(tan(ωW)×Ymax)≦33  (3)

Conditional expression (3) prescribes a condition to reduce the apertureof the first lens group and maintain an angle of view of 80° or greaterat the wide angle edge while realizing a zoom ratio of 8 or greater.Below the lower limit of conditional expression (3), although theaperture of the first lens group can be reduced and the angle of view atthe wide angle edge can be increased, a zoom ratio of 8 or greaterbecomes difficult to realize. On the other hand, beyond the upper limitof conditional expression (3), although a zoom ratio of 8 or greater canbe achieved, reduction of the aperture of the first lens group andincrease of the angle of view at the wide angle edge become difficult torealize.

As described, by satisfying conditional expression (1), the zoom lensaccording to the embodiment has a small aperture while being able tomaintain a wide angle of view of 80° or greater. Further, by satisfyingconditional expression (2), the zoom lens is compact and has a wideangle of view while being able to maintain high optical performance overthe entire zoom range. Additionally, by satisfying conditionalexpression (3), the zoom lens is able to be compact, have a wide angleof view and a high zoom ratio.

Favorable results can be expected by satisfying any one of theconditional expressions above, as described. Nonetheless, satisfactionof more than one of the conditional expressions above, as compared tosatisfaction of only one condition expression, further improves results.

Furthermore, the zoom lens according to the embodiment preferablysatisfies the following conditional expression, where a total thicknessalong the optical axis of the lens groups is ΣD, the half angle of viewof the optical system, at the wide angle edge is ωW, and the maximumparaxial image height at the wide angle edge is Ymax.3.5≦ΣD/(tan(ωW)×Ymax)≦5.5  (4)

Conditional expression (4) prescribes a condition for a suitable totalthickness along the optical axis of the lens groups to achieve a thinnerretracted-state size, while providing for a wide angle of view of 80° orgreater. Satisfaction of conditional expression (4) enables both anangle of view of 80° or greater and a thinner retracted-state size.Below the lower limit of conditional expression (4), such a thin lensthickness is called for the lens groups that lens processing becomesdifficult. Further, such a wide angle of view is called for thataberration correction for the angle of view becomes difficult. On theother hand, beyond the upper limit of conditional expression (4), thetotal thickness of the lens groups becomes too large, making a thinnerretracted-state size difficult to achieve.

The zoom lens according to the embodiment preferably satisfies thefollowing conditional expression, where the focal length of the secondlens group is F2, the focal length of the third lens group is F3, andthe focal length (infinity focus) of the entire optical system at thewide angle edge is FW.8.0≦|F2×F3|/FW≦15  (5)

Conditional expression (5) prescribes a condition to maintain an angleof view of 80° or greater at the wide angle edge, while achieving athinner retracted-state size and a high zoom ratio. Below the lowerlimit of conditional expression (5), although an angle of view of 80° orgreater at the wide angle edge can be maintained and a thinnerretracted-state size can be achieved, the refractive power of the secondlens group and of the third lens group becomes too strong, making thecorrection of various types of aberration difficult. On the other hand,beyond the upper limit of conditional expression (5), the refractivepower of the second lens group and of the third lens group becomes tooweak. If the realization of a high zoom ratio is attempted under suchconditions, displacement of the second lens group and of the third lensgroup has to be increased, which means that the cam barrel for movingthe lens groups has to be lengthened, whereby a thinner retracted-statesize becomes difficult to realize. Furthermore, if the refractive powerof the second lens and of the third lens is weak, an angle of view of80° or greater at the wide angle edge becomes difficult to achieve.

The zoom lens according to the embodiment preferably satisfies thefollowing conditional expression, where the focal length of the secondlens group is F2, a thickness along the direction of the optical axis ofthe second lens group is D2, and the maximum paraxial image height atthe wide angle edge is Ymax.5.0≦F2×D2|/Ymax≦10  (6)

Conditional expression (6) prescribes a condition for reducing thethickness of the second lens group and for a suitable refractive powerof the second lens group to realize a greater angle of view and athinner retracted-state size. Below the lower limit of conditionalexpression (6), the refractive power of the second lens group becomestoo strong, making the correction of various types of aberrationdifficult, which is undesirable. On the other hand, beyond the upperlimit of conditional expression (6), the refractive power of the secondlens group becomes too weak, making an angle of view of 80° or greaterdifficult to achieve. Further, the thickness of the second lens groupbecomes thick, making a thinner retracted-state size difficult torealize.

As described, the zoom lens according to the embodiment, in addition tomaintaining a wide angle of view, is able to realize a thinnerretracted-state size and a high zoom ratio. For example, satisfaction ofconditional expression (4) obtains a suitable total thickness along theoptical axis of the lens groups constituting the zoom lens and enables awide angle of view (80° or greater) and a thinner retracted-state sizeto be realized. Furthermore, satisfaction of conditional expression (5)obtains a suitable refractive power for the second lens group and of thethird lens group and enables a wide angle of view of 80° or greaterwhile further enabling a thinner retracted-state size and a high zoomratio to be achieved. In addition, satisfaction of conditionalexpression (6) enables a reduction in the thickness of the second lensgroup, obtains a suitable refractive power for the second lens group,and enables an increase of the angle of view and a thinnerretracted-state size.

Favorable results can be expected by satisfying any one of theconditional expressions above, as described. Nonetheless, satisfactionof more than one of the conditional expressions above, as compared tosatisfaction of only one condition expression, further improves results.

In the zoom lens according to the embodiment, the first lens groupincludes plural positive lenses. The zoom lens preferably satisfies thefollowing conditional expression, where with respect to the d-line ofthe positive lenses of the first lens group, the average Abbe number isλdP1 and the average refractive index is NdP1.25≦λdP1/NdP1≦35  (7)

Condition expression (7) prescribes a condition to maintain an angle ofview of 80° or greater at the wide angle edge, reduce the thickness ofthe first lens group and achieve satisfactory correction of chromaticaberration of magnification at the telephoto edge of the zoom lens.Below the lower limit of conditional expression (7), although areduction of the thickness of the first lens group is easily achieved,the correction of chromatic aberration of magnification with respect tolong wavelengths (C-line) at the telephoto edge becomes difficultachieve. On the other hand, beyond the upper limit of conditionalexpression (7), the refractive index with respect to the d-line of thepositive lenses in the first lens group has to be lowered and the Abbenumber has to be increased. If maintenance of a suitable refractivepower of the first lens group is attempted under such conditions, thethickness of the first lens group increases, making reductions inthickness difficult. Further, the correction of chromatic aberration ofmagnification with respect to short wavelengths (g-line) at thetelephoto edge becomes difficult achieve.

In the zoom lens according to the embodiment, the second lens groupincludes plural negative lenses including sequentially from the objectside, a first negative lens and a second negative lens. The zoom lenspreferably satisfies the following conditional expression, where withrespect to the d-line of the second negative lens, the Abbe number isλdM2and the refractive index is NdM2.20≦λdM2/NdM2≦31  (8)

Conditional expression (8) prescribes a condition to reduce thethickness of the second lens group and achieve satisfactory correctionof chromatic aberration of magnification at the wide angle edge of thezoom lens. Below the lower limit of conditional expression (8), althougha reduction in the thickness of the second lens group is easilyachieved, the correction of longitudinal chromatic aberration at thetelephoto edge becomes difficult. On the other hand, beyond the upperlimit of conditional expression (8), in order to maintain an appropriaterefractive power of the second lens group, the curvature of radius ofthe second negative lens has to be significantly increased, making areduction in the thickness of the second lens group difficult. Inaddition, satisfactory correction of spherical aberration andastigmatism in the zoom lens, as well as chromatic aberration ofmagnification with respect to short wavelengths (g-line) at the wideangle edge become difficult.

In the zoom lens according to the embodiment, the third lens groupincludes plural positive lenses. The zoom lens preferably satisfies thefollowing conditional expression, where with respect to the d-line ofthe positive lens that, among the lenses of the third lens group, isfarthest on the object side, the Abbe number is λdP3, and the refractiveindex is NdP3.2≦(λdM2/NdM2)−(λdP3/NdP3)≦12  (9)

Conditional expression (9) prescribes a condition to realize a high zoomratio (8 or greater) while achieving satisfactory correction ofchromatic aberration at the wide angle edge and at the telephoto edge.Below the lower limit of conditional expression (9), although thecorrection of chromatic aberration of magnification at the wide angleedge is easily achieved, the correction of longitudinal chromaticaberration at the telephoto edge becomes difficult. On the other hand,beyond the upper limit of conditional expression (9), although thecorrection of longitudinal chromatic aberration for short wavelengths atthe telephoto edge is easily achieved, the correction of chromaticaberration of magnification at the wide angle edge becomes difficult.

Additionally, in the zoom lens according to the embodiment, the secondlens group, in addition to the negative lenses, includes at least 1positive lens having an aspheric surface on the imaging plane side. Thezoom lens preferably satisfies the following conditional expression,where deviation of the paraxial curvature radius at a height that is 10%of the effective diameter of the aspheric surface and the aspheric shapeis S10, and the height of 10% of the effective diameter is H10.−0.1<S10/H10<−0.005  (10)

Conditional expression (10) prescribes the aspheric shape of a positivelens in the second lens group. By adopting in the second lens group, alens having an aspheric shape satisfying conditional expression (10),various types of aberration such as spherical aberration, astigmatism,and distortion can be corrected satisfactorily over the entire zoomrange. Below the lower limit of conditional expression (10), theinflection point of the aspheric shape becomes prominent, making lensprocessing difficult and causing problems with lens manufacture. On theother hand, beyond the upper limit of conditional expression (10), areduction in the size of the first lens group becomes difficult andsufficient correction of the various types of aberration cannot beachieved.

As described, satisfaction of conditional expression (7) maintains awide angle of view of 80° or greater, reduces the thickness of the firstlens group, and enables satisfactory correction of chromatic aberrationof magnification at the telephoto edge of the zoom lens. Satisfaction ofconditional expression (8) reduces the thickness of the second lensgroup and enables satisfactory correction of chromatic aberration ofmagnification at the wide angle edge of the zoom lens. Satisfaction ofconditional expression (9) realizes a high zoom ratio (8 or greater),while achieving satisfactory correction of chromatic aberration at thewide angle edge and at the telephoto edge. In addition, satisfaction ofconditional expression (10) enables further improvement of aberrationcorrection. Satisfaction of each of the conditional expressions aboveenables the zoom lens according to the embodiment to maintain a wideangle of view and high optical performance and have a thinnerretracted-state size and a high zoom ratio.

Favorable results can be expected by satisfying any one of theconditional expressions above, as described. Nonetheless, satisfactionof more than one of the conditional expressions above, as compared tosatisfaction of only one conditional expression, further improvesresults.

FIG. 1 is a cross sectional view (along the optical axis) of a zoom lensaccording to a first example. The zoom lens includes, sequentially froma non-depicted object side, a positive first lens group G₁₁, a negativesecond lens group G₁₂, a positive third lens group G₁₃ and a positivefourth lens group G₁₄. Further, a diaphragm STP is disposed between thesecond lens group G₁₂ and the third lens group G₁₃. A cover glass CG (orfilter) is disposed between the fourth lens group G₁₄ and an imagingplane IMG. The cover glass CG (or filter) is disposed as needed and maybe omitted when not necessary. Further, at the imaging plane IMG, anoptical receiving surface of an imaging element such as a CCD, a CMOS,etc. is disposed.

The first lens group G₁₁ includes sequentially from the object side, anegative lens L₁₁₁, a positive lens L₁₁₂, and a positive lens L₁₁₃. Thenegative lens L₁₁₁ and the positive lens L₁₁₂ are cemented together.

The second lens group G₁₂ includes sequentially from the object side, anegative lens L₁₂₁, a negative lens L₁₂₂, and a positive lens L₁₂₃. Bothsurfaces of the negative lens L₁₂₁ and a surface on the imaging planeIMG side of the positive lens L₁₂₃ are aspheric. Further, the negativelens L₁₂₂ and the positive lens L₁₂₃ are cemented together.

The third lens group G₁₃ includes sequentially from the object side, apositive lens L₁₃₁, a negative lens L₁₃₂, and a positive lens L₁₃₃. Asurface on the object side of the positive lens L₁₃₁ is aspheric.Further, the positive lens L₁₃₁ and the negative lens L₁₃₂ are cementedtogether.

The fourth lens group G₁₄ includes a positive lens L₁₄₁. Both surfacesof the positive lens L₁₄₁ are aspheric.

The zoom lens zooms from the wide angle edge to the telephoto edge bymoving the first lens group G₁₁, the second lens group G₁₂, and thethird lens group G₁₃ along the optical axis. Furthermore, the zoom lenscorrects imaging plane (image location) variation accompanying zoom andfocuses the image, by moving the fourth lens group G₁₄ along the opticalaxis.

Various values related to the zoom lens according to the first exampleare indicated below.

-   Focal length of zoom lens system=4.365 (wide angle edge) to 13.109    (intermediate zoom position) to 41.178 (telephoto edge)-   F number=3.58 (wide angle edge) to 4.84 (intermediate zoom position)    to 5.75 (telephoto edge)-   Angle of view (2ω)=87.6° (wide angle edge) to 33.6° (intermediate    zoom position) to 10.56° (telephoto edge)    (Values Related to Conditional Expression (1))-   At wide angle edge, interval between lens farthest on imaging plane    side among lenses of the second lens group G₁₂ and lens farthest on    object side among lenses of the third lens group G₁₃ (D23W)=11.532-   D23W/FW=2.64    (Values Related to Conditional Expression (2))-   Focal length of the first lens group G₁₁ (F1)=35.5194-   Focal length of the second lens group G₁₂ (F2)=−5.8942-   |F1/F2|=6.03    (Values Related to Conditional Expression (3))-   Total length of optical system, at wide angle edge (TaW)=38.5991-   Total length of optical system, at telephoto edge (TaT)=55.5311-   Half angle of view of optical system, at wide angle edge (ωW)=43.80-   Maximum paraxial image height at wide angle edge (Ymax)=4.1858-   (TaW+TaT)/(tan(ωW)×Ymax)=23.45-   r₁=42.4567    -   d₁=0.7000 nd₁=1.92286 νd₁=20.88-   r₂=23.7410    -   d₂=2.8893 nd₂=1.61800 νd₂=63.39-   r₃=123.2525    -   d₃=0.1500-   r₄=24.3075    -   d₄=2.2214 nd₃=1.88300 νd₃=40.80-   r₅=72.0512    -   d₅=0.5000 (wide angle edge) to 8.4947 (intermediate zoom        position) to 19.7731 (telephoto edge)-   r₆=18.2902 (aspheric surface)    -   d₆=0.8000 nd₄=1.85135 νd₄=40.10-   r₇=4.1413 (aspheric surface)    -   d₇=2.6217-   r₈=−104.4554    -   d₈=0.4500 nd₅=1.74330 νd₅=49.22-   r₉=8.5587    -   d₉=1.6559 nd₆=2.00170 νd₆=19.32-   r₁₀=31.8881 (aspheric surface)    -   d₁₀=11.1821 (wide angle edge) to 3.0587 (intermediate zoom        position) to 0.1871 (telephoto edge)-   r₁₁=∞ (diaphragm)    -   d₁₁=0.3500-   r₁₂=4.4041 (aspheric surface)    -   d₁₂=1.1356 nd₇=1.80611 νd₇=40.73-   r₁₃=8.7508    -   d₁₃=1.4251 nd₈=1.94595 νd₈=17.98-   r₁₄=4.0934    -   d₁₄=0.3433-   r₁₅=10.1848    -   d₁₅=1.1959 nd₉=1.61800 νd₉=63.39-   r₁₆=−10.1848    -   d₁₆=3.5000 (wide angle edge) to 5.7939 (intermediate zoom        position) to 13.5388 (telephoto edge)-   r₁₇=15.7815 (aspheric surface)    -   d₁₇=1.5000 nd₁₀=1.55332 νd₁₀=71.67-   r₁₈=−1000.0000 (aspheric surface)    -   d₁₈=4.4707 (wide angle edge) to 7.8402 (intermediate zoom        position) to 3.0627 (telephoto edge)-   r₁₉=∞    -   d₁₉=0.5000 nd₁₁=1.51680 νd₁₁=64.20-   r₂₀=∞    -   d₂₀=1.0081 (wide angle edge) to 1.0126 (intermediate zoom        position) to 1.0311 (telephoto edge)-   r₂₁=∞ (image plane)    Constant of cone (k) and Aspheric coefficients (A, B, C, D    (Sixth Plane)-   K=0,-   A=1.16028×10⁻⁴, B=−4.00446×10⁻⁵,-   C=9.99964×10⁻⁷, D=−7.76320×10⁻⁹    (Seventh Plane)-   K=−0.1858,-   A=6.53494×10⁻⁴, B=2.25949×10⁻⁵,-   C=−7.88249×10⁻⁶, D=7.04313×10⁻⁹    (Tenth Plane)-   K=0,-   A=−5.92227×10⁻⁴, B=4.38745×10⁻⁶,-   C=1.94199×10⁻⁷, D=−1.48702×10⁻⁹    (Twelfth Plane)-   K=−0.5353,-   A=9.52249×10⁻⁶, B=4.17341×10⁻⁵,-   C=−8.84871×10⁻⁶, D=1.17972×10⁻⁶    (Seventeenth Plane)-   K=−1.6970,-   A=−6.34973×10⁻⁴, B=3.53883×10⁻⁵,-   C=−2.81373×10⁻⁶, D=3.86441×10⁻⁸    (Eighteenth Plane)-   K=0,-   A=−6.44317×10⁻¹, B=1.51939×10⁻⁵,-   C=−1.68208×10⁻⁶, D=1.60171×10⁻⁸

FIG. 2 is a diagram of various types of aberration of the zoom lensaccording to the first example. In the diagram “g”, “d”, and “c”respectively represent aberrations for wavelengths corresponding tog-line (λ=435.83 nm), d-line (λ=587.56 nm), and c-line (λ=656.27 nm). Ina portion of FIG. 2 indicating astigmatism, ΔS and ΔM representaberration with respect to a sagittal image plane and a meridional imageplane, respectively.

FIG. 3 is a cross sectional view (along the optical axis) of a zoom lensaccording to a second example. The zoom lens includes, sequentially fromthe non-depicted object side, a positive first lens group G₂₁, anegative second lens group G₂₂, a positive third lens group G₂₃, and apositive fourth lens group G₂₄. Further, a diaphragm STP is disposedbetween the second lens group G₂₂ and the third lens group G₂₃. A coverglass CG (or filter) is disposed between the fourth lens group G₂₄ andthe imaging plane IMG. The cover glass CG (or filter) is disposed asneeded and may be omitted when not necessary. Further, at the imagingplane IMG, the optical receiving surface of an imaging element such as aCCD, a CMOS, etc. is disposed.

The first lens group G₂₁ includes sequentially from the object side, anegative lens L₂₁₁, a positive lens L₂₁₂, and a positive lens L₂₁₃. Thenegative lens L₂₁₁ and the positive lens L₂₁₂ are cemented together.

The second lens group G₂₂ includes sequentially from the object side, anegative lens L₂₂₁, a negative lens L₂₂₂, and a positive lens L₂₂₃. Bothsurfaces of the negative lens L₂₂₁ and a surface on the imaging planeIMG side of the positive lens L₂₂₃ are aspheric. Further, the negativelens L₂₂₂ and the positive lens L₂₂₃ are cemented together.

The third lens group G₂₃ includes sequentially from the object side, apositive lens L₂₃₁, a negative lens L₂₃₂, and a positive lens L₂₃₃. Asurface on the object side of the positive lens L₂₃₁ is aspheric.Further, the positive lens L₂₃₁ and the negative lens L₂₃₂ are cementedtogether.

The fourth lens group G₂₄ includes a positive lens L₂₄₁. Both surfacesof the positive lens L₂₄₁ are aspheric.

The zoom lens zooms from the wide angle edge to the telephoto edge bymoving the first lens group G₂₁, the second lens group G₂₂, and thethird lens group G₂₃ along the optical axis. Furthermore, the zoom lenscorrects imaging plane (image location) variation accompanying zoom andfocuses the image, by moving the fourth lens group G₂₄ along the opticalaxis.

Various values related to the zoom lens according to the second exampleare indicated below.

-   Focal length of zoom lens system=4.378 (wide angle edge) to 13.059    (intermediate zoom position) to 40.991 (telephoto edge)-   F number=3.58 (wide angle edge) to 4.88 (intermediate zoom position)    to 5.66 (telephoto edge)-   Angle of view (2ω)=87.4° (wide angle edge) to 33.12° (intermediate    zoom position) to 10.56° (telephoto edge)    (Values Related to Conditional Expression (1))-   At wide angle edge, interval between lens farthest on imaging plane    side among lenses of the second lens group G₂₂ and lens farthest on    object side among lenses of the third lens group G₂₃ (D23W)=11.363-   D23W/FW=2.60    (Values Related to Conditional Expression (2))-   Focal length of the first lens group G₂₁ (F1)=35.3573-   Focal length of the second lens group G₂₂ (F2)=−5.7182-   |F1/F2|=6.18    (Values Related to Conditional Expression (3))-   Total length of optical system, at wide angle edge (TaW)=38.7179-   Total length of optical system, at telephoto edge (TaT)=55.4904-   Half angle of view of optical system, at wide angle edge (ωW)=43.70-   Maximum paraxial image height at wide angle edge (Ymax)=4.1839-   (TaW+TaT)/(tan(ωW)×Ymax)=23.56-   r₁=35.3665    -   d₁=0.7000 nd₂=1.92286 νd₂=20.88-   r₂=22.7365    -   d₂=2.8303 nd₂=1.61800 νd₂=63.39-   r₃=94.1318    -   d₃=0.1500-   r₄=22.1345    -   d₄=2.1521 nd₃=1.78800 νd₃=47.49-   r₅=57.3854    -   d₅=0.5000 (wide angle edge) to 8.0817 (intermediate zoom        position) to 19.4548 (telephoto edge)-   r₆=19.8247 (aspheric surface)    -   d₆=0.8000 nd₄=1.85639 νd₄=40.10-   r₇=4.0732 (aspheric surface)    -   d₇=2.6721-   r₈=701.8212    -   d₈=0.4500 nd₅=1.77250 νd₅=49.62-   r₉=8.1000    -   d₉=1.6506 nd₆=2.01390 νd₆=19.32-   r₁₀=27.7772 (aspheric surface)    -   d₁₀=11.0131 (wide angle edge) to 3.0593 (intermediate zoom        position) to 0.1500 (telephoto edge)-   r₁₁=∞ (diaphragm)    -   d₁₁=0.3500-   r₁₂=4.6428 (aspheric surface)    -   d₁₂=1.3959 nd₇=1.80610 νd₇=40.74-   r₁₃=9.1218    -   d₁₃=1.2040 nd₈=1.94595 νd₈=17.98-   r₁₄=4.3311    -   d₁₄=0.3125-   r₁₅=9.9065    -   d₁₅=1.2138 nd₉=1.61800 νd₉=63.39-   r₁₆=−9.9065    -   d₁₆=4.2017 (wide angle edge) to 7.1778 (intermediate zoom        position) to 13.6497 (telephoto edge)-   r₁₇=16.9814 (aspheric surface)    -   d₁₇=1.5000 nd₁₀=1.55516 νd₁₀=71.67-   r₁₈=−224.2761 (aspheric surface)    -   d₁₈=4.1129 (wide angle edge) to 7.3262 (intermediate zoom        position) to 3.4643 (telephoto edge)-   r₁₉=∞    -   d₁₉=0.5000 nd₁₁=1.51680 νd₁₁=64.20-   r₂₀=∞    -   d₂₆=1.0090 (wide angle edge) to 0.9591 (intermediate zoom        position) to 0.8904 (telephoto edge)-   r₂₁=∞ (image plane)    Constant of cone (k) and Aspheric coefficients (A, B, C, D)    (Sixth Plane)-   K=0,-   A=1.09571×10⁻⁴, B=−2.97768×10⁻⁵,-   C=6.21695×10⁻⁷, D=−3.72502×10⁻⁹    (Seventh Plane)-   K=−0.1858,-   A=7.30061×10⁻⁴, B=3.77662×10⁻⁶,-   C=−3.03192×10⁻⁶, D=−1.86011×10⁻⁷    (Tenth Plane)-   K=0,-   A=−6.01399×10⁻⁴, B=3.30880×10⁻⁶,-   C=1.07 326×10⁻⁷, D=−4.56889×10⁻¹⁰    (Twelfth Plane)-   K=−0.5322,-   A=2.34771×10⁻⁵, B=1.08796×10⁻⁵,-   C=−1.60048×10⁻⁶, D=5.07288×10⁻⁷    (Seventeenth Plane)-   K=−4.3209,-   A=−6.78620×10⁻⁴, B=3.28433×10⁻⁵,-   C=−1.41788×10⁻⁶, D=−9.87708×10⁻⁹    (Eighteenth Plane)-   K=0,-   A=−8.87070×10⁻⁴, B=3.42 669×10⁻⁵,-   C=−1.76375×10⁻⁶, D=3.39007×10⁻⁹

FIG. 4 is a diagram of various types of aberration of the zoom lensaccording to the second example. In the diagram “g”, “d”, and “c”respectively represent aberrations for wavelengths corresponding tog-line (λ=435.83 nm), d-line (λ=587.56 nm), and c-line (λ=656.27 nm). Ina portion of FIG. 4 indicating astigmatism, ΔS and ΔM representaberration with respect to a sagittal image plane and a meridional imageplane, respectively.

FIG. 5 is a cross sectional view (along the optical axis) of a zoom lensaccording to a third example. The zoom lens includes, sequentially fromthe non-depicted object side, a positive first lens group G₃₁, anegative second lens group G₃₂, a positive third lens group G₃₃, and apositive fourth lens group G₃₄. Further, a diaphragm STP is disposedbetween the second lens group G₃₂ and the third lens group G₃₃. A coverglass CG (or filter) is disposed between the fourth lens group G₃₄ andthe imaging plane IMG. The cover glass CG (or filter) is disposed asneeded and may be omitted when not necessary. Further, at the imagingplane IMG, the optical receiving surface of an imaging element such as aCCD, a CMOS, etc. is disposed.

The first lens group G₃₁ includes sequentially from the object side, anegative lens L₃₁₁, a positive lens L₃₁₂, and a positive lens L₃₁₃. Thenegative lens L₃₁₁ and the positive lens L₃₁₂ are cemented together.

The second lens group G₃₂ includes sequentially from the object side, anegative lens L₃₂₁, a negative lens L₃₂₂, and a positive lens L₃₂₃. Bothsurfaces of the negative lens L₃₂₂ and a surface on the imaging planeIMG side of the positive lens L₃₂₃ are aspheric. Further, the negativelens L₃₂₂ and the positive lens L₃₂₃ are cemented together.

The third lens group G₃₃ includes sequentially from the object side, apositive lens L₃₃₁, a negative lens L₃₃₂, and a positive lens L₃₃₃. Asurface on the object side of the positive lens L₃₃₁ is aspheric.Further, the positive lens L₃₃₁ and the negative lens L₃₃₂ are cementedtogether.

The fourth lens group G₃₄ includes a positive lens L₃₄₁. Both surfacesof the positive lens L₃₄₁ are aspheric.

The zoom lens zooms from the wide angle edge to the telephoto edge bymoving the first lens group G₃₁, the second lens group G₃₂, and thethird lens group G₃₃ along the optical axis. Furthermore, the zoom lenscorrects imaging plane (image location) variation accompanying zoom andfocuses the image, by moving the fourth lens group G₃₄ along the opticalaxis.

Various values related to the zoom lens according to the third exampleare indicated below.

-   Focal length of zoom lens system=4.381 (wide angle edge) to 13.307    (intermediate zoom position) to 41.113 (telephoto edge)-   F number=3.60 (wide angle edge) to 4.82 (intermediate zoom position)    to 5.71 (telephoto edge)-   Angle of view (2ω)=87.4° (wide angle edge) to 33.12° (intermediate    zoom position) to 10.56° (telephoto edge)    (Values Related to Conditional Expression (1))-   At wide angle edge, interval between lens farthest on imaging plane    side among lenses of the second lens group G₃₂ and lens farthest on    object side among lenses of the third lens group G₃₃ (D23W)=10.771-   D23W/FW=2.50    (Values Related to Conditional Expression (2))-   Focal length of the first lens group G₃₁ (F1)=35.4149-   Focal length of the second lens group G₃₂ (F2)=−5.6003-   |F1/F2|=6.32    (Values Related to Conditional Expression (3))-   Total length of optical system, at wide angle edge (TaW)=38.1391-   Total length of optical system, at telephoto edge (TaT)=55.6475-   Half angle of view of optical system, at wide angle edge (ωW)=43.70-   Maximum paraxial image height at the wide angle edge (Ymax)=4.1861-   (TaW+TaT)/(tan(ωW)×Ymax)=23.45-   r₁=33.2686    -   d₁=0.8000 nd₁=1.84666 νd₁=23.78-   r₂=19.8000    -   d₂=3.0214 nd₂=1.61800 νd₂=63.39-   r₃=80.0497    -   d₃=0.1500-   r₄=24.5713    -   d₄=2.2786 nd₃=1.78800 νd₃=47.49-   r₅=78.2687    -   d₅=0.5000 (wide angle edge) to 9.5000 (intermediate zoom        position) to 19.6766 (telephoto edge)-   r₆=25.2886 (aspheric surface)    -   d₆=0.8000 nd₄=1.85135 νd₄=40.10-   r₇=4.1057 (aspheric surface)    -   d₇=2.4507-   r₈=562.3556    -   d₈=0.4500 nd₅=1.77250 νd₅=49.62-   r₉=8.5000    -   d₉=1.5324 nd₆=2.00170 νd₆=19.32-   r₁₀=31.7164 (aspheric surface)    -   d₁₀=10.4212 (wide angle edge) to 3.2143 (intermediate zoom        position) to 0.1500 (telephoto edge)-   r₁₁=∞ (diaphragm)    -   d₁₁=0.3500-   r₁₂=4.6699 (aspheric surface)    -   d₁₂=1.1969 nd₇=1.80610 νd₇=40.74-   r₁₃=9.2400    -   d₁₃=1.3621 nd₈=1.94595 νd₈=17.98-   r₁₄=4.4271    -   d₁₄=0.3144-   r₁₅=10.8758    -   d₁₅=1.2266 nd₉=1.61800 νd₉=63.39-   r₁₆=−9.1157    -   d₁₆=4.0000 (wide angle edge) to 7.1658 (intermediate zoom        position) to 13.6403 (telephoto edge)-   r₁₇=17.2904 (aspheric surface)    -   d₁₇=1.5000 nd₁₀=1.59201 νd₁₀=67.02-   r₁₈=−500.0000 (aspheric surface)    -   d₁₈=3.6718 (wide angle edge) to 6.6915 (intermediate zoom        position) to 3.2000 (telephoto edge)-   r₁₉=∞    -   d₁₉=0.5000 nd₁₁=1.51680 νd₁₁=64.20-   r₂₀=∞    -   d₂₀=1.6130 (wide angle edge) to 1.0391 (intermediate zoom        position) to 1.0475 (telephoto edge)-   r₂₁=∞ (image plane)    Constant of cone (k), and Aspheric coefficients (A, B, C, D)    (Sixth Plane)-   K=0,-   A=1.70699×10⁻⁴, B=−3.32288×10⁻⁵,-   C=7.95002×10⁻⁷, D=−6.27099×10⁻⁹    (Seventh Plane)-   K=−0.1858,-   A=8.43675×10⁻⁴, B=6.56293×10⁻⁶,-   C=−2.00670×10⁻⁶, D=−2.29541×10⁻⁷    (Tenth Plane)-   K=0,-   A=−5.64411×10⁻⁴, B=−1.75974×10⁻⁵,-   C=1.70798×10⁻⁶, D=−3.89949×10⁻⁸    (Twelfth Plane)-   K=−0.5973,-   A=−1.92725×10⁻⁵, B=8.22671×10⁻⁵,-   C=−2.28281×10⁻⁵, D=2.78115×10⁻⁶    (Seventeenth Plane)-   K=1.6141,-   A=−5.92164×10⁻⁴, B=1.68205×10⁻⁵,-   C=−7.73392×10⁻⁷, D=−2.40077×10⁻⁸    (Eighteenth Plane)-   K=0,-   A=−6.47064×10⁻⁴, B=2.16671×10⁻⁵,-   C=−1.42681×10⁻⁶, D=−6.03161×10⁻¹⁰

FIG. 6 is a diagram of various types of aberration of the zoom lensaccording to the third example. In the diagram “g”, “d”, and “c”respectively represent aberrations for wavelengths corresponding tog-line (λ=435.83 nm), d-line (λ=587.56 nm), and c-line (λ=656.27 nm). Ina portion of FIG. 6 indicating astigmatism, ΔS and ΔM representaberration with respect to a sagittal image plane and a meridional imageplane, respectively.

Among the values for the examples above, r₁, r₂, . . . indicate radii ofcurvature for each lens, diaphragm surface, etc.; d₁, d₂, . . . indicatethe thickness of the lenses, diaphragm, etc. or the distance betweensurfaces thereof; nd₁, nd₂, . . . indicate the refraction index of eachlens with respect to the d-line (λ=587.56 nm); νd₁, νd₂, . . . indicatethe Abbe number with respect to the d-line (λ=587.56 nm) of each lens.

Each of the aspheric surfaces above can be expressed by the equationhereinafter, where Z=the depth of the aspheric surface, y=the heightfrom the optical axis, and the direction of travel of light is positive.

$\begin{matrix}{Z = {\frac{y^{2}}{{R\left( {1 + \sqrt{1 - {\left( {1 + K} \right){y/R^{2}}}}} \right)}^{2}} + {Ay}^{4} + {By}^{6} + {Cy}^{8} + {Dy}^{10}}} & \lbrack 1\rbrack\end{matrix}$

Where, R is paraxial radii of curvature; K is constant of the cone; andA, B, C, D are the fourth, sixth, eighth, and tenth asphericcoefficients, respectively.

As described above, the zoom lens according to each of the examplesabove has a small aperture, has a wide angle of view (80° or greater),is able to maintain high optical performance over the entire zoom range,and has a high zoom ratio (8 or greater), by satisfying the conditionalexpressions above.

FIG. 7 is a cross sectional view (along the optical axis) of a zoom lensaccording to a fourth example. The zoom lens includes, sequentially fromthe non-depicted object side, a positive first lens group G₁₁, anegative second lens group G₁₂, a positive third lens group G₁₃, and apositive fourth lens group G₁₄. Further, a diaphragm STP is disposedbetween the second lens group G₁₂ and the third lens group G₁₃. A coverglass CG (or filter) is disposed between the fourth lens group G₁₄ andthe imaging plane IMG. The cover glass CG (or filter) is disposed asneeded and may be omitted when not necessary. Further, at the imagingplane IMG, the optical receiving surface of an imaging element such as aCCD, a CMOS, etc. is disposed.

The first lens group G₁₁ includes sequentially from the object side, anegative lens L₁₁₁, a positive lens L₁₁₂, and a positive lens L₁₁₃. Thenegative lens L₁₁₁ and the positive lens L₁₁₂ are cemented together.

The second lens group G₁₂ includes sequentially from the object side, anegative lens L₁₂₁, a negative lens L₁₂₂, and a positive lens L₁₂₃. Bothsurfaces of the negative lens L₁₂₁ and a surface on the imaging planeIMG side of the positive lens L₁₂₃ are aspheric. Further, the negativelens L₁₂₂ and the positive lens L₁₂₃ are cemented together.

The third lens group G₁₃ includes sequentially from the object side, apositive lens L₁₃₁, a negative lens L₁₃₂, and a positive lens L₁₃₃. Asurface on the object side of the positive lens L₁₃₁ is aspheric.Further, the positive lens L₁₃₁ and the negative lens L₁₃₂ are cementedtogether.

The fourth lens group G₁₄ includes a positive lens L₁₁₄. Both surfacesof the positive lens L₁₄₁ are aspheric.

The zoom lens zooms from the wide angle edge to the telephoto edge bymoving the first lens group G₁₁, the second lens group G₁₂, and thethird lens group G₁₃ along the optical axis. Furthermore, the zoom lenscorrects imaging plane (image location) variation accompanying zoom andfocuses the image, by moving the fourth lens group G₁₄ along the opticalaxis.

Various values related to the zoom lens according to the fourth exampleare indicated below.

-   Focal length of zoom lens system=4.365 (wide angle edge) to 13.109    (intermediate zoom position) to 41.178 (telephoto edge)-   F number=3.58 (wide angle edge) to 4.84 (intermediate zoom position)    to 5.75 (telephoto edge)-   Angle of view (2ω)=87.6° (wide angle edge) to 33.6° (intermediate    zoom position) to 10.56° (telephoto edge)    (Values Related to Conditional Expression (4))-   Total thickness along optical axis of lens groups (ΣD)=17.0882-   Half angle of view of optical system, at wide angle edge (ωW)=43.80-   Maximum paraxial image height at the wide angle edge (Ymax)=4.1858-   ΣD/(tan(ωW)×Ymax)=4.26    (Values Related to Conditional Expression (5))-   Focal length of the second lens group G₁₂ (F2)=−5.8942-   Focal length of the third lens group G₁₃ (F3)=8.9547    Focal length (infinity focus) of the entire optical system at wide    angle edge (FW)=4.3649-   |F2×F3|/FW=12.09    (Values Related to Conditional Expression (6))-   Focal length of the second lens group G₁₂ (F2)=−5.8942-   Thickness along direction of optical axis of the second lens group    G₁₂ (D2)=5.5275-   Maximum paraxial image height at the wide angle edge (Ymax)=4.1858-   |F2×D2|/Ymax=7.78-   r₁=42.4567    -   d₁=0.7000 nd₁=1.92286 νd₁=20.88-   r₂=23.7410    -   d₂=2.8893 nd₂=1.61800 νd₂=63.39-   r₃=123.2525    -   d₃=0.1500-   r₄=24.3075    -   d₄=2.2214 nd₃=1.88300 νd₃=40.80-   r₅=72.0512    -   d₅=0.5000 (wide angle edge) to 8.4947 (intermediate zoom        position) to 19.7731 (telephoto edge)-   r₆=18.2902 (aspheric surface)    -   d₆=0.8000 nd₄=1.85135 νd₄=40.10-   r₇=4.1413 (aspheric surface)    -   d₇=2.6217-   r₈=−104.4554    -   d₈=0.4500 nd₅=1.74330 νd₅=49.22-   r₉=8.5587    -   d₉=1.6559 nd₆=2.00170 νd₆=19.32-   r₁₀=31.8881 (aspheric surface)    -   d₁₀=11.1821 (wide angle edge) to 3.0587 (intermediate zoom        position) to 0.1871 (telephoto edge)-   r₁₁=∞ (diaphragm)    -   d₁₁=0.3500-   r₁₂=4.4041 (aspheric surface)    -   d₁₂=1.1356 nd₇=1.80611 νd₇=40.73-   r₁₃=8.7508    -   d₁₃=1.4251 nd₈=1.94595 νd₈=17.98-   r₁₄=4.0934    -   d₁₄=0.3433-   r₁₅=10.1848    -   d₁₅=1.1959 nd₉=1.61800 νd₉=63.39-   r₁₆=−10.1848    -   d₁₆=3.5000 (wide angle edge) to 5.7939 (intermediate zoom        position) to 13.5388 (telephoto edge)-   r₁₇=15.7815 (aspheric surface)    -   d₁₇=1.5000 nd₁₀=1.55332 νd₁₀=71.67-   r₁₈=−1000.0000 (aspheric surface)    -   d₁₈=4.4707 (wide angle edge) to 7.8402 (intermediate zoom        position) to 3.0627 (telephoto edge)-   r₁₉=∞    -   d₁₉=0.5000 nd₁₁=1.51680 νd₁₁=64.20-   r₂₀=∞    -   d₂₀=1.0081 (wide angle edge) to 1.0126 (intermediate zoom        position) to 1.0311 (telephoto edge)-   r₂₁=∞ (image plane)    Constant of cone (k) and Aspheric coefficients (A, B, C, D)    (Sixth Plane)-   K=0,-   A=1.16028×10⁻⁴, B=−4.00446×10⁻⁵,-   C=9.99964×10⁻⁷, D=−7.76320×10⁻⁹    (Seventh Plane)-   K=−0.1858,-   A=6.53494×10⁻⁴, B=2.25949×10⁻⁵,-   C=−7.88249×10⁻⁶, D=7.04313×10⁻⁵    (Tenth Plane)-   K=0,-   A=−5.92227×10⁻⁴, B=4.38745×10⁻⁶,-   C=1.94199×10⁻⁷, D=−1.48702×10⁻⁵    (Twelfth Plane)-   K=−0.5353,-   A=9.52249×10⁻⁶, B=4.17341×10⁻⁵,-   C=−8.84871×10⁻⁶, D=1.17972×10⁻⁶    (Seventeenth Plane)-   K=−1.6970,-   A=−6.34973×10⁻⁴, B=3.53883×10⁻⁵,-   C=−2.81373×10⁻⁶, D=3.86441×10⁻⁶    (Eighteenth Plane)-   K=0,-   A=−6.44317×10⁻⁴, B=1.51939×10⁻⁵,-   C=−1.68208×10⁻⁶, D=1.60171×10⁻⁵

FIG. 8 is a diagram of various types of aberration of the zoom lensaccording to the fourth example. In the diagram “g”, “d”, and “c”respectively represent aberrations for wavelengths corresponding tog-line (λ=435.83 nm), d-line (λ=587.56 nm), and c-line (λ=656.27 nm). Ina portion of FIG. 8 indicating astigmatism, ΔS and ΔM representaberration with respect to a sagittal image plane and a meridional imageplane, respectively.

FIG. 9 is a cross sectional view (along the optical axis) of a zoom lensaccording to a fifth example. The zoom lens includes, sequentially fromthe non-depicted object side, a positive first lens group G₂₁, anegative second lens group G₂₂, a positive third lens group G₂₃, and apositive fourth lens group G₂₄. Further, a diaphragm STP is disposedbetween the second lens group G₂₂ and the third lens group G₂₃. A coverglass CG (or filter) is disposed between the fourth lens group G₂₄ andthe imaging plane IMG. The cover glass CG (or filter) is disposed asneeded and may be omitted when not necessary. Further, at the imagingplane IMG, the optical receiving surface of an imaging element such as aCCD, a CMOS, etc. is disposed.

The first lens group G₂₁ includes sequentially from the object side, anegative lens L₂₁₁, a positive lens L₂₁₂, and a positive lens L₂₁₃. Thenegative lens L₂₁₁ and the positive lens L₂₁₂ are cemented together.

The second lens group G₂₂ includes sequentially from the object side, anegative lens L₂₂₁, a negative lens L₂₂₂, and a positive lens L₂₂₃. Bothsurfaces of the negative lens L₂₂₁ and a surface on the imaging planeIMG side of the positive lens L₂₂₃ are aspheric. Further, the negativelens L₂₂₂ and the positive lens L₂₂₃ are cemented together.

The third lens group G₂₃ includes sequentially from the object side, apositive lens L₂₃₁, a negative lens L₂₃₂, and a positive lens L₂₃₃. Asurface on the object side of the positive lens L₂₃₁ is aspheric.Further, the positive lens L₂₃₁ and the negative lens L₂₃₂ are cementedtogether.

The fourth lens group G₂₄ includes a positive lens L₂₄₁. Both surfacesof the positive lens L₂₄₁ are aspheric.

The zoom lens zooms from the wide angle edge to the telephoto edge bymoving the first lens group G₂₁, the second lens group G₂₂, and thethird lens group G₂₃ along the optical axis. Furthermore, the zoom lenscorrects imaging plane (image location) variation accompanying zoom andfocuses the image, by moving the fourth lens group G₂₄ along the opticalaxis.

Various values related to the zoom lens according to the fifth exampleare indicated below.

-   Focal length of zoom lens system=4.378 (wide angle edge) to 13.059    (intermediate zoom position) to 40.991 (telephoto edge)-   F number=3.58 (wide angle edge) to 4.88 (intermediate zoom position)    to 5.66 (telephoto edge)-   Angle of view (2ω)=87.4° (wide angle edge) to 33.12° (intermediate    zoom position) to 10.56° (telephoto edge)    (Values Related to Conditional Expression (4))-   Total thickness along optical axis of lens groups (ΣD)=17.0313-   Half angle of view of optical system, at wide angle edge (ωW)=43.70-   Maximum paraxial image height at the wide angle edge (Ymax)=4.1839-   ΣD/(tan(ωW)×Ymax)=4.26    (Values Related to Conditional Expression (5))-   Focal length of the second lens group G₂₂ (F2)=−5.7182-   Focal length of the third lens group G₂₃ (F3)=8.8889-   Focal length (infinity focus) of the entire optical system at wide    angle edge (FW)=4.3782-   |F2×F3|/FW=11.61    (Values Related to Conditional Expression (6))    Focal length of the second lens group G₂₂ (F2)=−5.7182-   Thickness along direction of optical axis of the second lens group    G₂₂ (D2)=5.5727-   Maximum paraxial image height at the wide angle edge (Ymax)=4.1839-   |F2×D2|/Ymax=7.62-   r₁=35.3665    -   d₁=0.7000 nd₁=1.92286 νd₁=20.88-   r₂=22.7365    -   d₂=2.8303 nd₂=1.61800 νd₂=63.39-   r₃=94.1318    -   d₃=0.1500-   r₄=22.1345    -   d₄=2.1521 nd₃=1.78800 νd₃=47.49-   r₅=57.3854    -   d₅=0.5000 (wide angle edge) to 8.0817 (intermediate zoom        position) to 19.4548 (telephoto edge)-   r₆=19.8247 (aspheric surface)    -   d₆=0.8000 nd₄=1.85639 νd₄=40.10-   r₇=4.0732 (aspheric surface)    -   d₇=2.6721-   r₈=701.8212    -   d₈=0.4500 nd₅=1.77250 νd₅=49.62-   r₉=8.1000    -   d₉=1.6506 nd₆=2.01390 νd₆=19.32-   r₁₀=27.7772 (aspheric surface)    -   d₁₀=11.0131 (wide angle edge) to 3.0593 (intermediate zoom        position) to 0.1500 (telephoto edge)-   r₁₁=∞ (diaphragm)    -   d₁₁=0.3500-   r₁₂=4.6428 (aspheric surface)    -   d₁₂=1.3959 nd₇=1.80610 νd₇=40.74-   r₁₃=9.1218    -   d₁₃=1.2040 nd₈=1.94595 νd₈=17.98-   r₁₄=4.3311    -   d₁₄=0.3125-   r₁₅=9.9065    -   d₁₅=1.2138 nd₉=1.61800 νd₉=63.39-   r₁₆=−9.9065    -   d₁₆=4.2017 (wide angle edge) to 7.1778 (intermediate zoom        position) to 13.6497 (telephoto edge)-   r₁₇=16.9814 (aspheric surface)    -   d₁₇=1.5000 nd₁₀=1.55516 νd₁₀=71.67-   r₁₈=−224.2761 (aspheric surface)    -   d₁₈=4.1129 (wide angle edge) to 7.3262 (intermediate zoom        position) to 3.4643 (telephoto edge)-   r₁₉=∞    -   d₁₉=0.5000 nd₁₁=1.51680 νd₁₁=64.20-   r₂₀=∞    -   d₂₀=1.0090 (wide angle edge) to 0.9591 (intermediate zoom        position) to 0.8904 (telephoto edge)-   r₂₁=∞ (image plane)    Constant of cone (k) and Aspheric coefficients (A, B, C, D    (Sixth Plane)-   K=0,-   A=1.09571×10⁻⁴, B=−2.97768×10⁻⁵,-   C=6.21695×10⁻⁷, D=−3.72502×10⁻⁹    (Seventh Plane)-   K=−0.1858,-   A=7.30061×10⁻⁴, B=3.77662×10⁻⁶,-   C=−3.03192×10⁻⁶, D=−1.86011×10⁻⁷    (Tenth Plane)-   K=0,-   A=−6.01399×10⁻⁴, B=3.30880×10⁻⁶,-   C=1.07326×10⁻⁷, D=−4.56889×10⁻¹⁰    (Twelfth Plane)-   K=−0.5322,-   A=2.34771×10⁻⁵, B=1.08796×10⁻⁵,-   C=−1.60048×10⁻⁶, D=5.07288×10⁻⁷    (Seventeenth Plane)-   K=−4.3209,-   A=−6.78620×10⁻⁴, B=3.28433×10⁻⁵,-   C=−1.41788×10⁻⁶, D=−9.87708×10⁻⁹    (Eighteenth Plane)-   K=0,-   A=−8.87070×10⁻⁴, B=3.42669×10⁻⁵,-   C=−1.76375×10⁻⁶, D=3.39007×10⁻⁹

FIG. 10 is a diagram of various types of aberration of the zoom lensaccording to the fifth example. In the diagram “g”, “d”, and “c”respectively represent aberrations for wavelengths corresponding tog-line (λ=435.83 nm), d-line (λ=587.56 nm), and c-line (λ=656.27 nm). Ina portion of FIG. 10 indicating astigmatism, ΔS and ΔM representaberration with respect to a sagittal image plane and a meridional imageplane, respectively.

FIG. 11 is a cross sectional view (along the optical axis) of a zoomlens according to a sixth example. The zoom lens includes, sequentiallyfrom the non-depicted object side, a positive first lens group G₃₁, anegative second lens group G₃₂, a positive third lens group G₃₃, and apositive fourth lens group G₃₄. Further, a diaphragm STP is disposedbetween the second lens group G₃₂ and the third lens group G₃₃. A coverglass CG (or filter) is disposed between the fourth lens group G₃₄ andthe imaging plane IMG. The cover glass CG (or filter) is disposed asneeded and may be omitted when not necessary. Further, at the imagingplane IMG, an optical receiving surface of an imaging element such as aCCD, a CMOS, etc. is disposed.

The first lens group G₃₁ includes sequentially from the object side, anegative lens L₃₁₁, a positive lens L₃₁₂, and a positive lens L₃₁₃. Thenegative lens L₃₁₁ and the positive lens L₃₁₂ are cemented together.

The second lens group G₃₂ includes sequentially from the object side, anegative lens L₃₂₁, a negative lens L₃₂₂, and a positive lens L₃₂₃. Bothsurfaces of the negative lens L₃₂₁ and a surface on the imaging planeIMG side of the positive lens L₃₂₃ are aspheric. Further, the negativelens L₃₂₂ and the positive lens L₃₂₃ are cemented together.

The third lens group G₃₃ includes sequentially from the object side, apositive lens L₃₃₁, a negative lens L₃₃₂, and a positive lens L₃₃₃. Asurface on the object side of the positive lens L₃₃₁ is aspheric.Further, the positive lens L₃₃₁ and the negative lens L₃₃₂ are cementedtogether.

The fourth lens group G₃₄ includes a positive lens L₃₄₁. Both surfacesof the positive lens L₃₄₁ are aspheric.

The zoom lens zooms from the wide angle edge to the telephoto edge bymoving the first lens group G₃₁, the second lens group G₃₂, and thethird lens group G₃₃ along the optical axis. Furthermore, the zoom lenscorrects imaging plane (image location) variation accompanying zoom andfocuses the image, by moving the fourth lens group G₃₄ along the opticalaxis.

Various values related to the zoom lens according to the sixth exampleare indicated below.

-   Focal length of zoom lens system=4.381 (wide angle edge) to 13.307    (intermediate zoom position) to 41.113 (telephoto edge)-   F number=3.60 (wide angle edge) to 4.82 (intermediate zoom position)    to 5.71 (telephoto edge)-   Angle of view (2ω)=87.4° (wide angle edge) to 33.12° (intermediate    zoom position) to 10.56° (telephoto edge)    (Values Related to Conditional Expression (4))-   Total thickness along optical axis of lens groups (ΣD)=17.0831-   Half angle of view of optical system, at wide angle edge (ωW)=43.70-   Maximum paraxial image height at the wide angle edge (Ymax)=4.1861-   ΣD/(tan(ωW)×Ymax)=4.27    (Values Related to Conditional Expression (5))-   Focal length of the second lens group G₃₂ (F2)=−5.6003-   Focal length of the third lens group G₃₃ (F3)=8.7461-   Focal length (infinity focus) of entire optical system at wide angle    edge (FW)=4.3805-   |F2×F3|/FW=11.18    (Values Related to Conditional Expression (6))-   Focal length of the second lens group G₃₂ (F2)=−5.6003-   Thickness along direction of optical axis of the second lens group    G₃₂ (D2)=5.2331-   Maximum paraxial image height at the wide angle edge (Ymax)=4.1861-   |F2×D2|/Ymax=7.00-   r₁=33.2686    -   d₁=0.8000 nd₁=1.84666 νd₁=23.78-   r₂=19.8000    -   d₂=3.0214 nd₂=1.61800 νd₂=63.39-   r₃=80.0497    -   d₃=0.1500-   r₄=24.5713    -   d₄=2.2786 nd₃=1.78800 νd₃=47.49-   r₅=78.2687    -   d₅=0.5000 (wide angle edge) to 9.5000 (intermediate zoom        position) to 19.6766 (telephoto edge)-   r₆=25.2886 (aspheric surface)    -   d₆=0.8000 nd₄=1.85135 νd₄=40.10-   r₇=4.1057 (aspheric surface)    -   d₇=2.4507-   r₈=562.3556    -   d₈=0.4500 nd₅=1.77250 νd₅=49.62-   r₉=8.5000    -   d₉=1.5324 nd₆=2.00170 νd₆=19.32-   r₁₀=31.7164 (aspheric surface)    -   d₁₀=10.4212 (wide angle edge) to 3.2143 (intermediate zoom        position) to 0.1500 (telephoto edge)-   r₁₁=∞ (diaphragm)    -   d₁₁=0.3500-   r₁₂=4.6699 (aspheric surface)    -   d₁₂=1.1969 nd₇=1.80610 νd₇=40.74-   r₁₃=9.2400    -   d₁₃=1.3621 nd₆=1.94595 νd₈=17.98-   r₁₄=4.4271    -   d₁₄=0.3144-   r₁₅=10.8758    -   d₁₅=1.2266 nd₉=1.61800 νd₉=63.39-   r₁₆=−9.1157    -   d₁₆=4.0000 (wide angle edge) to 7.1658 (intermediate zoom        position) to 13.6403 (telephoto edge)-   r₁₇=17.2904 (aspheric surface)    -   d₁₇=1.5000 nd₁₀=1.59201 νd₁₀=67.02-   r₁₈=−500.0000 (aspheric surface)    -   d₁₈=3.6718 (wide angle edge) to 6.6915 (intermediate zoom        position) to 3.2000 (telephoto edge)-   r₁₉=∞    -   d₁₉=0.5000 nd₁₁=1.51680 νd₁₁=64.20-   r₂₀=∞    -   d₂₀=1.6130 (wide angle edge) to 1.0391 (intermediate zoom        position) to 1.0475 (telephoto edge)-   r₂₁=∞ (image plane)    Constant of cone (k), and Aspheric coefficients (A, B, C, D)    (Sixth Plane)-   K=0,-   A=1.70699×10⁻⁴, B=−3.32288×10⁻⁵,-   C=7.95002×10⁻⁷, D=−6.27099×10⁻⁹    (Seventh Plane)-   K=−0.1858,-   A=8.43675×10⁻⁴, B=6.56293×10⁻⁶,-   C=−2.00670×10⁻⁶, D=−2.29541×10⁻⁷    (Tenth Plane)-   K=0,-   A=−5.64411×10⁻⁴, B=−1.75974×10⁻⁵,-   C=1.70798×10⁻⁶, D=−3.89949×10⁻⁹    (Twelfth Plane)-   K=−0.5973,-   A=−1.92725×10⁻⁵, B=8.22671×10⁻⁵,-   C=−2.28281×10⁻⁵, D=2.78115×10⁻⁶    (Seventeenth Plane)-   K=1.6141,-   A=−5.92164×10⁻⁴, B=1.68205×10⁻⁵,-   C=−7.73392×10⁻⁷, D=−2.40077×10⁻⁸    (Eighteenth Plane)-   K=0,-   A=−6.47064×10⁻⁴, B=2.16671×10⁻⁵,-   C=−1.42681×10⁻⁶, D=−6.03161×10⁻¹⁰

FIG. 12 is a diagram of various types of aberration of the zoom lensaccording to the sixth example. In the diagram “g”, “d”, and “c”respectively represent aberrations for wavelengths corresponding tog-line (λ=435.83 nm), d-line (λ=587.56 nm), and c-line (λ=656.27 nm). Ina portion of FIG. 12 indicating astigmatism, ΔS and ΔM representaberration with respect to a sagittal image plane and a meridional imageplane, respectively.

Among the values for the examples above, r₁, r₂, . . . indicate radii ofcurvature for each lens, diaphragm surface, etc.; d₁, d₂, . . . indicatethe thickness of the lenses, diaphragm, etc. or the distance betweensurfaces thereof; nd₁, nd₂, . . . indicate the refraction index of eachlens with respect to the d-line (λ=587.56 nm); νd₁, νd₂, . . . indicatethe Abbe number with respect to the d-line (λ=587.56 nm) of each lens.

Each of the aspheric surfaces above can be expressed by the equationhereinafter, where Z=the depth of the aspheric surface, y=the heightfrom the optical axis, and the direction of travel of light is positive.

$\begin{matrix}{Z = {\frac{y^{2}}{{R\left( {1 + \sqrt{1 - {\left( {1 + K} \right){y/R^{2}}}}} \right)}^{2}} + {Ay}^{4} + {By}^{6} + {Cy}^{8} + {Dy}^{10}}} & \lbrack 1\rbrack\end{matrix}$

Where, R is paraxial radii of curvature; K is constant of the cone; andA, B, C, D are the fourth, sixth, eighth, and tenth asphericcoefficients, respectively.

As described above, the zoom lens according to each of the examplesabove realizes a thinner retracted-state size and an increased angle ofview (80° or greater) while having a high zoom ratio (8 or greater) bysatisfying the conditional expressions above. Since a lens having asuitable aspheric surface is employed, satisfactory optical performancecan be maintained with fewer lenses.

FIG. 13 is a cross sectional view (along the optical axis) of a zoomlens according to a seventh example. The zoom lens includes,sequentially from the non-depicted object side, a positive first lensgroup G₁₁, a negative second lens group G₁₂, a positive third lens groupG₁₃, and a positive fourth lens group G₁₄. Further, a diaphragm STP isdisposed between the second lens group G₁₂ and the third lens group G₁₃.A cover glass CG (or filter) is disposed between the fourth lens groupG₁₄ and the imaging plane IMG. The cover glass CG (or filter) isdisposed as needed and may be omitted when not necessary. Further, atthe imaging plane IMG, the optical receiving surface of an imagingelement such as a CCD, a CMOS, etc. is disposed.

The first lens group G₁₁ includes sequentially from the object side, anegative lens L₁₁₁, a positive lens L₁₁₂, and a positive lens L₁₁₃. Thenegative lens L₁₁₁ and the positive lens L₁₁₂ are cemented together.

The second lens group G₁₂ includes sequentially from the object side, anegative lens L₁₂₁ (first negative lens), a negative lens L₁₂₂ (secondnegative lens), and a positive lens L₁₂₃. Both surfaces of the negativelens L₁₂₁ and a surface on the imaging plane IMG side of the positivelens L₁₂₃ are aspheric. Further, the negative lens L₁₂₂ and the positivelens L₁₂₃ are cemented together.

The third lens group G₁₃ includes sequentially from the object side, apositive lens L₁₃₁, a negative lens L₁₃₂, and a positive lens L₁₃₃. Asurface on the object side of the positive lens L₁₃₁ is aspheric.Further, the positive lens L₁₃₁ and the negative lens L₁₃₂ are cementedtogether.

The fourth lens group G₁₄ includes a positive lens L₁₄₁. Both surfacesof the positive lens L₁₄₁ are aspheric.

The zoom lens zooms from the wide angle edge to the telephoto edge bymoving the first lens group G₁₁, the second lens group G₁₂, and thethird lens group G₁₃ along the optical axis. Furthermore, the zoom lenscorrects imaging plane (image location) variation accompanying zoom andfocuses the image, by moving the fourth lens group G₁₄ along the opticalaxis.

Various values related to the zoom lens according to the seventh exampleare indicated below.

-   Focal length of zoom lens system=4.365 (wide angle edge) to 13.109    (intermediate zoom position) to 41.178 (telephoto edge)-   F number=3.58 (wide angle edge) to 4.82 (intermediate zoom position)    to 5.75 (telephoto edge)-   Angle of view (2ω)=87.6° (wide angle edge) to 33.6° (intermediate    zoom position) to 10.56° (telephoto edge)    (Values Related to Conditional Expression (7))-   Average Abbe number with respect to d-line of positive lenses    (positive lens L₁₁₂, positive lens L₁₁₃) of the first lens group G₁₁    (λdP1)=52.0500-   Average refractive index with respect to d-line of positive lens    (positive lens L₁₁₂, positive lens L₁₁₃) of the first lens group G₁    (NdP1)=1.7505-   λdP1/NdP1=29.73    (Values Related to Conditional Expression (8))-   Abbe number with respect to d-line of second negative lens (negative    lens L₁₂₂) (λdM2)=49.2000-   Refractive index with respect to d-line of second negative lens    (negative lens L₁₂₂) (NdM2)=1.7433-   λdM2/NdM2=28.22    (Values Related to Conditional Expression (9))-   Abbe number with respect to d-line of positive lens (positive lens    L₁₃₁) that among lenses of the third lens group G₁₃ is farthest on    object side (λdP3)=40.7000-   Refractive index with respect to d-line of positive lens (positive    lens L₁₃₁) that among lenses of the third lens group G₁₃ is farthest    on object side (NdP3)=1.8061-   (λdM2NdM2)−(λdP3/NdP3)=5.69    (Values Related to Conditional Expression (10))-   Deviation of paraxial curvature radius at height that is 10% of the    effective diameter of aspheric surface on the imaging plane IMG side    of the positive lens L₁₂₃ in the second lens group G₁₂ and the    aspheric shape (S10)=−0.1000-   Height of 10% of effective diameter of the aspheric surface on the    imaging plane IMG side of the positive lens L₁₂₃ in the second lens    group G₁₂ (H10)=3.7-   S10/H10=−0.0270-   r₁=42.4567    -   d₁=0.7000 nd₁=1.92286 νd₁=20.88-   r₂=23.7410    -   d₂=2.8893 nd₂=1.61800 νd₂=63.39-   r₃=123.2525    -   d₃=0.1500-   r₄=24.3075    -   d₄=2.2214 nd₃=1.88300 νd₃=40.80-   r₅=72.0512    -   d₅=0.5000 (wide angle edge) to 8.4947 (intermediate zoom        position) to 19.7731 (telephoto edge)-   r₆=18.2902 (aspheric surface)    -   d₆=0.8000 nd₄=1.85135 νd₄=40.10-   r₇=4.1413 (aspheric surface)    -   d₇=2.6217-   r₉=−104.4554    -   d₈=0.4500 nd₅=1.74330 νd₅=49.22-   r₉=8.5587    -   d₉=1.6559 nd₆=2.00170 νd₆=19.32-   r₁₀=31.8881 (aspheric surface)    -   d₁₀=11.1821 (wide angle edge) to 3.0587 (intermediate zoom        position) to 0.1871 (telephoto edge)-   r₁₁=∞ (diaphragm)    -   d₁₁=0.3500-   r₁₂=4.4041 (aspheric surface)    -   d₁₂=1.1356 nd₇=1.80611 νd₇=40.73-   r₁₃=8.7508    -   d₁₃=1.4251 nd_(B)=1.94595 νd₈=17.98-   r₁₄=4.0934    -   d₁₄=0.3433-   r₁₅=10.1848    -   d₁₅=1.1959 nd₉=1.61800 νd₉=63.39-   r₁₆=−10.1848    -   d₁₆=3.5000 (wide angle edge) to 5.7939 (intermediate zoom        position) to 13.5388 (telephoto edge)-   r₁₇=15.7815 (aspheric surface)    -   d₁₇=1.5000 nd₁₀=1.55332 νd₁₀=71.67-   r₁₆=−1000.0000 (aspheric surface)    -   d₁₈=4.4707 (wide angle edge) to 7.8402 (intermediate zoom        position) to 3.0627 (telephoto edge)-   r₁₉=∞    -   d₁₉=0.5000 nd₁₁=1.51680 νd₁₁=64.20-   r₂₀=∞    -   d₂₀=1.0081 (wide angle edge) to 1.0126 (intermediate zoom        position) to 1.0311 (telephoto edge)-   r₂₁=∞ (image plane)    Constant of cone (k), and Aspheric coefficients (A, B, C, D)    (Sixth Plane)-   K=0,-   A=1.16028×10⁻⁴, B=−4.00446×10⁻⁵,-   C=9.99964×10⁻⁷, D=−7.76320×10⁻⁹    (Seventh Plane)-   K=−0.1858,-   A=6.53494×10⁻⁴, B=2.25949×10⁻⁵,-   C=−7.88249×10⁻⁶, D=7.04313×10⁻⁹    (Tenth Plane)-   K=0,-   A=−5.92227×10⁻⁴, B=4.38745×10⁻⁶,-   C=1.94199×10⁻⁷, D=−1.48702×10⁻⁹    (Twelfth Plane)-   K=−0.5353,-   A=9.52249×10⁻⁶, B=4.17341×10⁻⁵,-   C=−8.84871×10⁻⁶, D=1.17972×10⁻⁶    (Seventeenth Plane)-   K=−1.6970,-   A=−6.34973×10⁻⁴, B=3.53883×10⁻⁵,-   C=−2.81373×10⁻⁶, D=3.86441×10⁻⁸    (Eighteenth Plane)-   K=0,-   A=−6.44317×10⁻⁴, B=1.51939×10⁻⁵,-   C=−1.68208×10⁻⁶, D=1.60171×10⁻⁸

FIG. 14 is a diagram of various types of aberration of the zoom lensaccording to the seventh example. In the diagram “g”, “d”, and “c”respectively represent aberrations for wavelengths corresponding tog-line (λ=435.83 nm), d-line (λ=587.56 nm), and c-line (λ=656.27 nm). Ina portion of FIG. 14 indicating astigmatism, ΔS and ΔM representaberration with respect to a sagittal image plane and a meridional imageplane, respectively.

FIG. 15 is a cross sectional view (along the optical axis) of a zoomlens according to an eighth example. The zoom lens includes,sequentially from the non-depicted object side, a positive first lensgroup G₂₁, a negative second lens group G₂₂, a positive third lens groupG₂₃, and a positive fourth lens group G₂₄. Further, a diaphragm STP isdisposed between the second lens group G₂₂ and the third lens group G₂₃.A cover glass CG (or filter) is disposed between the fourth lens groupG₂₄ and the imaging plane IMG. The cover glass CG (or filter) isdisposed as needed and may be omitted when not necessary. Further, atthe imaging plane IMG, the optical receiving surface of an imagingelement such as a CCD, a CMOS, etc. is disposed.

The first lens group G₂₁ includes sequentially from the object side, anegative lens L₂₁₁, a positive lens L₂₁₂, and a positive lens L₂₁₃. Thenegative lens L₂₁₁ and the positive lens L₂₁₂ are cemented together.

The second lens group G₂₂ includes sequentially from the object side, anegative lens L₂₂₁ (first negative lens), a negative lens L₂₂₂ (secondnegative lens), and a positive lens L₂₂₃. Both surfaces of the negativelens L₂₂₁ and a surface on the imaging plane IMG side of the positivelens L₂₂₃ are aspheric. Further, the negative lens L₂₂₂ and the positivelens L₂₂₃ are cemented together.

The third lens group G₂₃ includes sequentially from the object side, apositive lens L₂₃₁, a negative lens L₂₃₂, and a positive lens L₂₃₃. Asurface on the object side of the positive lens L₂₃₁ is aspheric.Further, the positive lens L₂₃₁ and the negative lens L₂₃₂ are cementedtogether.

The fourth lens group G₂₄ includes a positive lens L₂₄₁. Both surfacesof the positive lens L₂₄₁ are aspheric.

The zoom lens zooms from the wide angle edge to the telephoto edge bymoving the first lens group G₂₁, the second lens group G₂₂, and thethird lens group G₂₃ along the optical axis. Furthermore, the zoom lenscorrects imaging plane (image location) variation accompanying zoom andfocuses the image, by moving the fourth lens group G₂₄ along the opticalaxis.

Various values related to the zoom lens according to the eighth exampleare indicated below.

-   Focal length of zoom lens system=4.378 (wide angle edge) to 13.059    (intermediate zoom position) to 40.991 (telephoto edge)-   F number=3.58 (wide angle edge) to 4.82 (intermediate zoom position)    to 5.66 (telephoto edge)-   Angle of view (2ω)=87.4° (wide angle edge) to 33.12° (intermediate    zoom position) to 10.56° (telephoto edge)    (Values Related to Conditional Expression (7))-   Average Abbe number with respect to d-line of positive lenses    (positive lens L₂₁₂, positive lens L₂₁₃) in the first lens group G₂₁    (λdP1)=55.3500-   Average refraction index with respect to d-line of positive lenses    (positive lens L₂₁₂, positive lens L₂₁₃) in the first lens group G₂₁    (NdP1)=1.7030-   λdP1/NdP1=32.50    (Values Related to Conditional Expression (8))-   Abbe number with respect to d-line of second negative lens (negative    lens L₂₂₂) (λdM2)=49.6000-   Refractive index with respect to d-line of second negative lens    (negative lens L₂₂₂) (NdM2)=1.7725-   λdM2/ NdM2=27.98    (Values Related to Conditional Expression (9))-   Abbe number with respect to d-line of positive lens (positive lens    L₂₃₁) that among lenses of the third lens group G₂₃, is farthest on    object side (λdP3)=40.7000-   Refractive index with respect to d-line of positive lens (positive    lens L₂₃₁) that among lenses of the third lens group G₂₃, is    farthest on object side (NdP3)=1.8061-   (λdM2/NdM2)−(λdP3/NdP3)=5.45    (Values Related to Conditional Expression (10))-   Deviation of paraxial curvature radius at height that is 10% of    effective diameter of aspheric surface on the imaging plane IMG side    of positive lens L₂₂₃ in the second lens group G₂₂ and the aspheric    shape (S10)=−0.0909-   Height of 10% of effective diameter of the aspheric surface on the    imaging plane IMG side of the positive lens L₂₂₃ in the second lens    group G₂₂ (H10)=3.6-   S10/H10=−0.0253-   r₁=35.3665    -   d₁=0.7000 nd₁=1.92286 νd₁=20.88-   r₂=22.7365    -   d₂=2.8303 nd₂=1.61800 νd₂=63.39-   r₃=94.1318    -   d₃=0.1500-   r₄=22.1345    -   d₄=2.1521 nd₃=1.78800 νd₃=47.49-   r₅=57.3854    -   d₅=0.5000 (wide angle edge) to 8.0817 (intermediate zoom        position) to 19.4548 (telephoto edge)-   r₆=19.8247 (aspheric surface)    -   d₆=0.8000 nd₄=1.85639 νd₄=40.10-   r₇=4.0732 (aspheric surface)    -   d₇=2.6721-   r₈=701.8212    -   d₈=0.4500 nd₅=1.77250 νd₅=49.62-   r₉=8.1000    -   d₉=1.6506 nd₆=2.01390 νd₆=19.32-   r₁₀=27.7772 (aspheric surface)    -   d₁₀=11.0131 (wide angle edge) to 3.0593 (intermediate zoom        position) to 0.1500 (telephoto edge)-   r₁₁=∞ (diaphragm)    -   d₁₁=0.3500-   r₁₂=4.6428 (aspheric surface)    -   d₁₂=1.3959 nd₇=1.80610 νd₇=40.74-   r₁₃=9.1218    -   d₁₃=1.2040 nd₈=1.94595 νd₈=17.98-   r₁₄=4.3311    -   d₁₄=0.3125-   r₁₅=9.9065    -   d₁₅=1.2138 nd₉=1.61800 νd₉=63.39-   r₁₆=−9.9065    -   d₁₆=4.2017 (wide angle edge) to 7.1778 (intermediate zoom        position) to 13.6497 (telephoto edge)-   r₁₇=16.9814 (aspheric surface)    -   d₁₇=1.5000 nd₁₀=1.55516 νd₁₀=71.67-   r₁₈=−224.2761 (aspheric surface)    -   d₁₈=4.1129 (wide angle edge) to 7.3262 (intermediate zoom        position) to 3.4643 (telephoto edge)-   r₁₉=∞    -   d₁₉=0.5000 nd₁₁=1.51680 νd₁₁=64.20-   r₂₀=∞    -   d₂₀=1.0090 (wide angle edge) to 0.9591 (intermediate zoom        position) to 0.8904 (telephoto edge)-   r₂₁=∞ (image plane)    Constant of cone (k), and Aspheric coefficients (A, B, C, D)    (Sixth Plane)-   K=0,-   A=1.09571×10⁻⁴, B=−2.97768×10⁻⁵,-   C=6.21695×10⁻⁷, D=−3.72502×10⁻⁹    (Seventh Plane)-   K=−0.1858,-   A=7.30061×10⁻⁴, B=3.77662×10⁻⁶,-   C=−3.03192×10⁻⁶, D=−1.86011×10⁻⁷    (Tenth Plane)-   K=0,-   A=−6.01399×10⁻⁴, B=3.30880×10⁻⁶,-   C=1.07326×10⁻⁷, D=−4.56889×10⁻¹⁰    (Twelfth Plane)-   K=−0.5322,-   A=2.34771×10⁻⁵, B=1.08796×10⁻⁵,-   C=−1.60048×10⁻⁶, D=5.07288×10⁻⁷    (Seventeenth Plane)-   K=−4.3209,-   A=−6.78620×10⁻⁴, B=3.28433×10⁻⁵,-   C=−1.41788×10⁻⁶, D=−9.87708×10⁻⁹    (Eighteenth Plane)-   K=0,-   A=−8.87070×10⁻⁴, B=3.42669×10⁻⁵,-   C=−1.76375×10⁻⁶, D=3.39007×10⁻⁹

FIG. 16 is a diagram of various types of aberration of the zoom lensaccording to the eighth example. In the diagram “g”, “d”, and “c”respectively represent aberrations for wavelengths corresponding tog-line (λ=435.83 nm), d-line (λ=587.56 nm), and c-line (λ=656.27 nm). Ina portion of FIG. 16 indicating astigmatism, ΔS and ΔM representaberration with respect to a sagittal image plane and a meridional imageplane, respectively.

FIG. 17 is a cross sectional view (along the optical axis) of a zoomlens according to a ninth example. The zoom lens includes, sequentiallyfrom the non-depicted object side, a positive first lens group G₃₁, anegative second lens group G₃₂, a positive third lens group G₃₃, and apositive fourth lens group G₃₄. Further, a diaphragm STP is disposedbetween the second lens group G₃₂ and the third lens group G₃₃. A coverglass CG (or filter) is disposed between the fourth lens group G₃₄ andthe imaging plane IMG. The cover glass CG (or filter) is disposed asneeded and may be omitted when not necessary. Further, at the imagingplane IMG, the optical receiving surface of an imaging element such as aCCD, a CMOS, etc. is disposed.

The first lens group G₃₁ includes sequentially from the object side, anegative lens L₃₁₁, a positive lens L₃₁₂, and a positive lens L₃₁₃. Thenegative lens L₃₁₁ and the positive lens L₃₁₂ are cemented together.

The second lens group G₃₂ includes sequentially from the object side, anegative lens L₃₂₁ (first negative lens), a negative lens L₃₂₂ (secondnegative lens), and a positive lens L₃₂₃. Both surfaces of the negativelens L₃₂₁ and a surface on the imaging plane IMG side of the positivelens L₃₂₃ are aspheric. Further, the negative lens L₃₂₂ and the positivelens L₃₂₃ are cemented together.

The third lens group G₃₃ includes sequentially from the object side, apositive lens L₃₃₁, a negative lens L₃₃₂, and a positive lens L₃₃₃. Asurface on the object side of the positive lens L₃₃₁ is aspheric.Further, the positive lens L₃₃₁ and the negative lens L₃₃₂ are cementedtogether.

The fourth lens group G₃₄ includes a positive lens L₃₄₁. Both surfacesof the positive lens L₃₄₁ are aspheric.

The zoom lens zooms from the wide angle edge to the telephoto edge bymoving the first lens group G₃₁, the second lens group G₃₂, and thethird lens group G₃₃ along the optical axis. Furthermore, the zoom lenscorrects imaging plane (image location) variation accompanying zoom andfocuses the image, by moving the fourth lens group G₃₄ along the opticalaxis.

Various values related to the zoom lens according to the ninth exampleare indicated below.

-   Focal length of zoom lens system=4.381 (wide angle edge) to 13.307    (intermediate zoom position) to 41.113 (telephoto edge)-   F number=3.60 (wide angle edge) to 4.82 (intermediate zoom position)    to 5.71 (telephoto edge)-   Angle of view (2ω)=87.4° (wide angle edge) to 33.12° (intermediate    zoom position) to 10.56° (telephoto edge)    (Values Related to Conditional Expression (7))-   Average Abbe number with respect to d-line of positive lenses    (positive lens L₃₁₂, positive lens L₃₁₃) in the first lens group G₃₁    (λdP1)=55.3500-   Average refraction index with respect to d-line of positive lenses    (positive lens L₃₁₂, positive lens L₃₁₃) in the first lens group G₃₁    (NdP1)=1.7030-   λdP1/NdP1=32.50    (Values Related to Conditional Expression (8))-   Abbe number with respect to d-line of second negative lens (negative    lens L₃₂₂) (λdM2)=49.6000-   Refractive index with respect to d-line of second negative lens    (negative lens L₃₂₂) (NdM2)=1.7725-   λdM2/NdM2=27.98    (Values Related to Conditional Expression (9))-   Abbe number with respect to d-line of positive lens (positive lens    L₃₃₁) that among lenses of the third lens group G₃₃, is farthest on    object side (λdP3)=40.7000-   Refractive index with respect to d-line of positive lens (positive    lens L₃₃₁) that among lenses of the third lens group G₃₃, is    farthest on object side (NdP3)=1.8061-   (λdM2/NdM2)−(λdP3/NdP3)=5.45    (Values Related to Conditional Expression (10))-   Deviation of paraxial curvature radius at height that is 10% of the    effective diameter of aspheric surface on the imaging plane IMG side    of the positive lens L₃₂₃ in the second lens group G₃₂ and the    aspheric shape (S10)=−0.0893-   Height of 10% of effective diameter of the aspheric surface on the    imaging plane IMG side of the positive lens L₃₂₃ in the second lens    group G₃₂ (H10)=3.5-   S10/H10=−0.0255-   r₁=33.2686    -   d₁=0.8000 nd₁=1.84666 νd₁=23.78-   r₂=19.8000    -   d₂=3.0214 nd₂=1.61800 νd₂=63.39-   r₃=80.0497    -   d₃=0.1500-   r₄=24.5713    -   d₄=2.2786 nd₃=1.78800 νd₃=47.49-   r₅=78.2687    -   d₅=0.5000 (wide angle edge) to 9.5000 (intermediate zoom        position) to 19.6766 (telephoto edge)-   r₆=25.2886 (aspheric surface)    -   d₆=0.8000 nd₄=1.85135 νd₄=40.10-   r₇=4.1057 (aspheric surface)    -   d₇=2.4507-   r₈=562.3556    -   d₈=0.4500 nd₅=1.77250 νd₅=49.62-   r₉=8.5000    -   d₉=1.5324 nd₆=2.00170 νd₆=19.32-   r₁₀=31.7164 (aspheric surface)    -   d₁₀=10.4212 (wide angle edge) to 3.2143 (intermediate zoom        position) to 0.1500 (telephoto edge)-   r₁₁=∞ (diaphragm)    -   d₁₁=0.3500-   r₁₂=4.6699 (aspheric surface)    -   d₁₂=1.1969 nd₇=1.80610 νd₇=40.74-   r₁₃=9.2400    -   d₁₃=1.3621 nd₈=1.94595 νd₈=17.98-   r₁₄=4.4271    -   d₁₄=0.3144-   r₁₅=10.8758    -   d₁₅=1.2266 nd₉=1.61800 νd₉=63.39-   r₁₆=−9.1157    -   d₁₆=4.0000 (wide angle edge) to 7.1658 (intermediate zoom        position) to 13.6403 (telephoto edge)-   r₁₇=17.2904 (aspheric surface)    -   d₁₇=1.5000 nd₁₀=1.59201 νd₁₀=67.02-   r₁₈=−500.0000 (aspheric surface)    -   d₁₈=3.6718 (wide angle edge) to 6.6915 (intermediate zoom        position) to 3.2000 (telephoto edge)-   r₁₉=∞    -   d₁₉=0.5000 nd₁₁=1.51680 νd₁₁=64.20-   r₂₀=∞    -   d₂₀=1.6130 (wide angle edge) to 1.0391 (intermediate zoom        position) to 1.0475 (telephoto edge)-   r₂₁=∞ (image plane)    Constant of cone (k), and Aspheric coefficients (A, B, C, D)    (Sixth Plane)-   K=0,-   A=1.70699×10⁻⁴, B=−3.32288×10⁻⁵,-   C=7.95002×10⁻⁷, D=−6.27099×10⁻⁹    (Seventh Plane)-   K=−0.1858,-   A=8.43675×10⁻⁴, B=6.56293×10⁻⁶,-   C=−2.00670×10⁻⁶, D=−2.29541×10⁻⁷    (Tenth Plane)-   K=0,-   A=−5.64411×10⁻⁴, B=−1.75974×10⁻⁵,-   C=1.70798×10⁻⁶, D=−3.89949×10⁻⁸    (Twelfth Plane)-   K=−0.5973,-   A=−1.92725×10⁻⁵, B=8.22671×10⁻⁵,-   C=−2.28281×10⁻⁵, D=2.78115×10⁻⁶    (Seventeenth Plane)-   K=1.6141,-   A=−5.92164×10⁻⁴, B=1.68205×10⁻⁵,-   C=−7.73392×10⁻⁷, D=−2.40077×10⁻⁸    (Eighteenth Plane)-   K=0,-   A=−6.47064×10⁻⁴, B=2.16671×10⁻⁵,-   C=−1.42681×10⁻⁶, D=−6.03161×10⁻¹⁰

FIG. 18 is a diagram of various types of aberration of the zoom lensaccording to the ninth example. In the diagram “g”, “d”, and “c”respectively represent aberrations for wavelengths corresponding tog-line (λ=435.83 nm), d-line (λ=587.56 nm), and c-line (λ=656.27 nm). Ina portion of FIG. 18 indicating astigmatism, ΔS and ΔM representaberration with respect to a sagittal image plane and a meridional imageplane, respectively.

Among the values for the examples above, r₁, r₂, . . . indicate radii ofcurvature for each lens, diaphragm surface, etc.; d₁, d₂, . . . indicatethe thickness of the lenses, diaphragm, etc. or the distance betweensurfaces thereof; nd₁, nd₂, . . . indicate the refraction index of eachlens with respect to the d-line (λ=587.56 nm); ν₁, νd₂, . . . indicatethe Abbe number with respect to the d-line (λ=587.56 nm) of each lens.

Each of the aspheric surfaces above can be expressed by the equationhereinafter, where Z=the depth of the aspheric surface, y=the heightfrom the optical axis, and the direction of travel of light is positive.

$\begin{matrix}{Z = {\frac{y^{2}}{{R\left( {1 + \sqrt{1 - {\left( {1 + K} \right){y/R^{2}}}}} \right)}^{2}} + {Ay}^{4} + {By}^{6} + {Cy}^{8} + {Dy}^{10}}} & \lbrack 1\rbrack\end{matrix}$

Where, R is paraxial radii of curvature; K is constant of the cone; andA, B, C, D are the fourth, sixth, eighth, and tenth asphericcoefficients, respectively.

As described above, the zoom lens according to each of the examplesabove is able to have a wide angle of view of 80° or greater, highoptical performance, a thinner retracted-state size, and a zoom ratio of8 or greater by satisfying the conditional expressions above. Further,since a lens having a suitable aspheric surface is employed, the zoomlens according to each of the examples can maintain satisfactory opticalperformance with fewer lenses.

Although the invention has been described with respect to a specificembodiment for a complete and clear disclosure, the appended claims arenot to be thus limited but are to be construed as embodying allmodifications and alternative constructions that may occur to oneskilled in the art which fairly fall within the basic teaching hereinset forth.

1. A zoom lens comprising, sequentially from an object side: a positivefirst lens group; a negative second lens group; a positive third lensgroup; and a positive fourth lens group, wherein 2.0≦D23W/FW≦3.0 issatisfied, D23W being an interval, at a wide angle edge, between a lensthat among lenses of the second lens group, is farthest on an imagingplane side and a lens that among lenses of the third lens group, isfarthest on the object side, FW being a focal length of an opticalsystem of the zoom lens at infinity focus, at the wide angle edge, andwherein 15≦(TaW+TaT)/(tan(ωW)×Ymax)≦33 is satisfied, TaW being a totallength of the optical system, at the wide angle, from a surface fartheston the object side to an imaging plane edge, TaT being a total length ofthe optical system, at a telephoto edge, from the surface farthest onthe object side to an imaging plane, ωW being a half angle of view ofthe optical system, at the wide angle edge, and Ymax being a maximumparaxial image height at the wide angle edge.
 2. The zoom lens accordingto claim 1, wherein 5.7≦|F1/F2|≦10 is satisfied, F1being a focal lengthof the first lens group and F2being a focal length of the second lensgroup.
 3. A zoom lens comprising, sequentially from an object side: apositive first lens group; a negative second lens group; a positivethird lens group; and a positive fourth lens group, wherein3.5≦ΣD/(tan(ωW)×Ymax)≦5.5 is satisfied, ΣD being a total thickness alongan optical axis of the first, the second, the third, and the fourth lensgroups, ωW being a half angle of view of an optical system of the zoomlens, at a wide angle edge, and Ymax being a maximum paraxial imageheight at the wide angle edge.
 4. The zoom lens according to claim 3,wherein 8.0≦|F2×F3|/FW≦15 is satisfied, F2being a focal length of thesecond lens group, F3being a focal length of the third lens group, andFW being a focal length of the optical system at infinity focus, at thewide angle edge.
 5. The zoom lens according to claim 3, wherein5.0≦|F2×D2|/Ymax≦10 is satisfied, F2being the focal length of the secondlens group, D2being a thickness along an optical axis of the second lensgroup, and Ymax being the maximum paraxial image height at the wideangle edge.
 6. The zoom lens according to claim 4, wherein5.0≦|F2×D2|/Ymax≦10 is satisfied, F2being the focal length of the secondlens group, D2being the thickness along an optical axis of the secondlens group, and Ymax being the maximum paraxial image height at the wideangle edge.
 7. A zoom lens comprising, sequentially from an object side:a positive first lens group; a negative second lens group; a positivethird lens group; and a positive fourth lens group, wherein the firstlens group includes plural positive lenses, and 25 ≦λdP1/NdP1≦35 issatisfied, λdP1being an average Abbe number with respect to a d-line ofthe positive lenses of the first lens group and NdP1 being an averagerefractive index with respect to the d-line of the positive lenses ofthe first lens group, and wherein the second lens group includes a firstnegative lens and a second negative lens, and 20≦λdM2/NdM2≦31 issatisfied, λdM2 being an Abbe number with respect to a d-line of thesecond negative lens and NdM2being a refractive index with respect tothe d-line of the second negative lens.
 8. The zoom lens according toclaim 7, wherein the second lens group includes sequentially from theobject side, the first negative lens and the second negative lens, thethird lens group includes plural positive lenses, and2≦(λdM2/NdM2)−(λdP3/NdP3)≦12 is satisfied, λdM2being the Abbe numberwith respect to the d-line of the second negative lens, NdM2being therefractive index with respect to the d-line of the second negative lens,λdP3being an Abbe number with respect to a d-line of a positive lensthat is farthest on the object side among the positive lenses of thethird lens group, and NdP3is a refractive index with respect to thed-line of the positive lens that is farthest on the object side amongthe lenses of the third lens group.
 9. A zoom lens comprising,sequentially from an object side: a positive first lens group; anegative second lens group; a positive third lens group; and a positivefourth lens group, wherein 2.0≦D23W/FW≦2.64 is satisfied, D23W being aninterval, at a wide angle edge, between a lens that among lenses of thesecond lens group, is farthest on an imaging plane side and a lens thatamong lenses of the third lens group, is farthest on the object side, FWbeing a focal length of an optical system of the zoom lens at infinityfocus, at the wide angle edge.
 10. A zoom lens comprising, sequentiallyfrom an object side: a positive first lens group; a negative second lensgroup; a positive third lens group; and a positive fourth lens group,wherein the first lens group includes plural positive lenses, and29.73≦λdP1/ NdP1≦35 is satisfied, λdP1 being an average Abbe number withrespect to a d-line of the positive lenses of the first lens group andNdP1 being an average refractive index with respect to the d-line of thepositive lenses of the first lens group.